Human Genomics. Writing in RED indicates the SQA outcomes. Writing in BLACK explains these outcomes in depth.

Bioinformatics is the use of computer technology to identify DNA sequences. The enormous amount of data produced by DNA and protein sequencing can be managed and analysed using computer technology and shared over the internet. Computer programs can be used to identify gene sequences by looking for coding sequences similar to known genes, start sequences or sequences lacking stop codons. Computer programs can be used to identify base sequences that correspond to the amino acid sequence of a protein Bioinformatics Bioinformatics is the use of computers to sequence DNA and to store and analyse the vast amount of information on DNA base sequences and amino acid sequences of proteins. An organism’s genome is the base sequence of its entire DNA. Genomics is the study of genomes. As well as the human genome, the genome of many other organisms important to humans has been found, e.g. those of crop plants and farm animals, of organisms used in genetic research, e.g. fruit flies and of many simple prokaryote organisms, e.g. E. coli. The importance of this is shown by the fact that many genes associated with cancer in humans have also been found in fruit flies – finding out how these genes work in a much simpler organism (fruit fly) can provide better understanding of their role in humans and may help to prevent or control certain cancers. Gene sequences can be identified by searching the genome for: Protein coding sequences that are the same as or similar to those of genes whose sequence is already known – the new base sequence will then have the same or similar function to the known gene. Known start sequences – because these are followed by coding sequences Long base sequences without stop codons (protein coding sequences are usually long and have a stop sequence only at the end)

Systematics compares human genome sequence data and genomes of other species to provide information on evolutionary relationships and origins. Systematics Systematics compares human genome sequence data with each other and with data from other species. Findings include: DNA of humans varies significantly less than that of other primates indicating that we evolved later (since there has been less time for mutations to occur) The greatest amount of variations in DNA are found in populations in Africa supporting the theory that the oldest human populations are found in Africa, i.e. that our species began there. When comparing species the more recently two species evolved from a common ancestor, the less their DNA varies.

Personalised medicine is based on an individual’s genome. Analysis of an individual’s genome may lead to personalised medicine through understanding the genetic component of risk of disease The importance of distinguishing between neutral and harmful mutations and the complex nature of many diseases. Pharmacogenetics and the use of genome information in the choice of effective drugs. Personalised medicine Sequencing an individual’s DNA is becoming faster and cheaper. Finding genes associated with disease conditions could allow an individual to adopt lifestyle changes that make it less likely that the disease will develop. Not all mutations found in the genome are harmful (can cause a disease condition) some mutations are neutral and have no negative effect on the individual. Pharmacogenetics Through the study of pharmaceutical drugs on genetically different individuals, it may be possible in future to tailor drugs and dosages to each individual making them more effective and reducing the possibility of side effects.

Amplification and detection of DNA sequences. Polymerase Chain Reaction (PCR) amplification of DNA using complementary primers for specific target sequences. DNA heated to separate strands then cooled for primer binding. Heat-tolerant DNA polymerase then replicates the region of DNA. Repeated cycles of heating and cooling amplify this region of DNA. Amplification of DNA Amplification involves making many copies of a DNA sample. This may be done: For genetic testing for medical purposes For forensic testing (genetic fingerprinting) For research, e.g. testing DNA of extinct species. Polymerase chain reaction (PCR) PCR is the method used to amplify a DNA sample.

Heat o C Cool to 54 o C Heat 72 o C Stages in the polymerase chain reaction (PCR) 1.Denaturing – DNA heated to separate (denature) the double stranded DNA 2.Annealing – Cooling allows primers (short sections of single stranded DNA) to bind (anneal) to either side of the part of the DNA molecule to be amplified (copied). [The primers bind by forming hydrogen bonds with complementary bases on the DNA strands] 3. DNA extension Heating allows the enzyme taq polymerase to add nucleotides to the 3’ ends of primers forming new DNA strands After one cycle the target DNA has been copied. Repeated cycles of heating and cooling makes multiple copies. primer Taq polymerase nucleotides primer

DNA probes are used to detect the presence of specific sequences in samples of DNA. The probes are short single stranded fragments of DNA that are complementary to a specific sequence. Fluorescent labelling allows detection. DNA probes A DNA probe is a short length of DNA with a known base sequence the is able to bind to a complementary base sequence on a DNA strand. DNA probes are “tagged” either by containing radioactive phosphate (which can be detected using X ray film) or by fluorescent labels (detected using laser scanning) DNA probes can be used to indicate the position of a gene on a length of DNA.

Applications of DNA profiling allow the identification of individuals through comparison of regions of the genome with highly variable numbers of repetitive sequences of DNA. DNA profiling Each persons DNA is unique (except in the case of identical twins). One way in which their DNA differs is in the number of tandem repeats found in the DNA. Tandem repeats are short non-coding regions of DNA composed of a number of repeating nucleotide base sequences. Tandem repeats are randomly distributed throughout the genome. They vary from person to person in their length (i.e. the number of times the base sequences are repeated) When DNA is digested into fragments before testing, the length of these fragments varies from one person to another depending on the number of tandem repeats each person’s DNA has. When the fragments are separated by gel electrophoresis each persons DNA has a unique pattern of bands (obtained by adding radioactive material and photographing the separated DNA fragments) In summary, what allows DNA profiling is the unique number of tandem repeats each person’s DNA has.